Method and device for controlling an internal combustion engine

ABSTRACT

A method and a device are described for controlling an internal combustion engine, particularly for controlling the injected fuel quantity. Starting from operating parameters, a variable being able to be specified that characterizes the fuel quantity, starting from which, activating signals for an actuator are specified. Starting from the rotary speed, the variable characterizing the fuel quantity and a variable characterizing the start of delivery, a correcting value for the correction of the variable characterizing the fuel quantity is specified.

FIELD OF THE INVENTION

The present invention relates to a method and a device for controllingan internal combustion engine, particularly for controlling the injectedfuel quantity. In the control of internal combustion engines, startingfrom operating parameters, a variable is specified that characterizesthe fuel quantity. The variable characterizing the fuel quantitypreferably concerns the fuel quantity, the duration of control for aactuator or another variable that characterizes the fuel quantity to beinjected, such as the torque. Starting from this variable thatcharacterizes the fuel quantity, control signals are specified for oneor more actuators that influence the fuel metering.

BACKGROUND INFORMATION

As actuators, especially so-called pump-nozzle units are used, in whichthe pressure buildup and the control of the injected fuel quantity takeplace in a structural unit, or pump-line-nozzle systems are used.Correspondingly, as actuator, an injector may also be used to which thefuel is supplied under high pressure, and the injector merely controlsthe fuel metering.

Usually such actuators are encumbered with tolerances. This means that,for the same control signal, different injectors meter in different fuelquantities. Furthermore, tolerances are able to have the effect that, inresponse to the same operating conditions, for the same control signal,different fuel quantities are metered in.

SUMMARY OF THE INVENTION

Because, starting from the rotary speed, from a variable characterizingthe fuel quantity and from a variable characterizing the start ofdelivery, a correcting value for correcting the variable characterizingthe fuel quantity is specified, tolerances, especially in the field ofactuators, may be clearly reduced. This results in clearly more accuratefuel metering and thereby lower emissions.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a block diagram of the device according to the presentinvention.

DETAILED DESCRIPTION

A quantity specification 100 specifies a quantity QK characterizing thefuel quantity to be injected. This usually reaches a controlspecification 110, which converts this signal into control signals forcontrolling a actuator 120. Corresponding methods and devices are knownand are usually converted in engine control devices.

Output signal QK of the quantity specification, output signal N of afirst sensor 130, output signal FB of a start of delivery control 135make their way to an adjustment characteristics map 140, and outputsignal SW of a threshold value specification 150 reach a minimumselection 160. The output signal of minimum selection 160 reaches amaximum selection 170, at whose second input there is present the outputsignal of a sign change 180, that also has signal SW of threshold valuespecification 150 applied to it. A node 105 has applied to it outputsignal K of maximum selection 170, and at its second input the outputsignal of quantity specification 100 is present. Output signal QKK ofnode 105 is then applied to a control specification 110, which, in turn,correspondingly activates actuator 120.

As a rule, these elements are components of a control unit whichactivates the actuator. In internal combustion engines having severalactuators, the elements should be designed in multiple fashion.

In adjustment characteristics map 140, as a function of variousvariables, correcting values K are stored, using which the fuel quantityQK to be injected is corrected. This correction is made in such a waythat tolerances of the individual actuators are adjusted, that is,correcting values K are specified in such a way that all actuatorsmeasure in the same fuel quantity in response to the same signal of thequantity specification. Furthermore, correcting values K are specifiedin such a way that a actuator, at the same operating condition,especially at the same rotary speed, at the same start of delivery andat the same output signal QK of the quantity specification, meters inthe same fuel quantity.

In this connection, it is particularly advantageous that, besides thefuel quantity and/or rotary speed N, in addition a signal thatcharacterizes the start of delivery, is drawn upon to specify correctingvalue K. This is advantageous especially in systems in which the startof delivery influences the fuel quantity to be injected. This is so, inparticular, in the case of so-called pump-nozzle systems and/or in thecase of so-called pump-line-nozzle systems. As the signal thatcharacterizes the start of delivery, preferably a signal is used thatindicates the angular position of the crankshaft or the camshaft, atwhich the injection begins. Alternatively, signals may also be used thatindicate the beginning of the activation of the actuator.

Instead of the fuel quantity QK to be injected, alternatively a torquequantity, a signal that characterizes the duration of control, oranother signal that characterizes the fuel quantity to be injected, maybe used.

It is usually provided that an adjustment characteristics map 140 isassigned to each actuator, that is, to each pump-nozzle system. In thiscontext, it is provided that the adjustment characteristics map isascertained subsequently to the manufacture of the actuator. The datathus ascertained are then assigned to the actuator in a suitable manner,and, when the actuator is put into operation for the first time, thedata are read into the control unit for the control of the internalcombustion engine, and are stored in a suitable manner. During runningoperation, the correction according to the present invention then takesplace based on these stored values.

In this context, various alternatives may be provided. On the one hand,the complete characteristics map may be ascertained, assigned to theactuator and then stored. On the other hand, it is possible to determinecorrecting values only at individual operating points, and to assignthese to the actuator. During first operation, starting from theseindividual correcting values, the remaining characteristics map valuesmay then be ascertained by using a suitable method. Alternatively, itmay also be provided that the calculation takes place constantly. Thisprocedure offers the advantage that only some few values have to beascertained and assigned to the actuator.

The assignment of the data to the actuator may be developed in differentways. It may be provided, for instance, that the actuator and a datacarrier, in which the data are inscribed, form a structural unit. On theother hand, it may be provided that the actuator and a data carrier,that includes an identification number, form a structural unit, and thatthen, in the light of this identification number, data are selectedwhich, using another data carrier and/or a transmission means, aretransmitted and then supplied to the control unit.

In one preferred specific embodiment, the output signals of theadjustment characteristics map are limited to maximum and minimumadmissible values. For this, minimum selection 160 and maximum selection170 are provided. Threshold value specification 150 specifies athreshold value which is directly supplied to the minimum selection and,with an inverted sign, to maximum selection 170. The result is that theoutput signal of the adjustment characteristics map is limited to amaximum absolute value by minimum selection 160 and maximum selection170. This is of advantage particularly if the values of the adjustmentcharacteristics map is calculated starting from a few test points. Inthat case it may happen that, on account of calculating accuracies andother effects, very large or very small correcting values occur, thatshould not be taken into consideration.

1-8. (canceled)
 9. A method for controlling an internal combustionengine, including for controlling a fuel quantity injected, comprising:starting from operating parameters, specifying a variable thatcharacterizes the fuel quantity, starting from which activating signalsfor an actuator are specified; and starting from a rotary speed, thevariable characterizing the fuel quantity, and a variable characterizinga start of delivery, specifying correcting values for correcting thevariable characterizing the fuel quantity.
 10. The method as recited inclaim 9, further comprising: storing the correcting values in acharacteristics map.
 11. The method as recited in claim 9, wherein thecorrecting values are specified individually for the respectiveactuator.
 12. The method as recited in claim 9, further comprising:ascertaining for each actuator and assigning thereto one of thecorrecting values and data starting from which the correcting values aredetermined.
 13. The method as recited in claim 9, further comprising:ascertaining subsequently to a manufacture of the actuator one of thecorrecting values and data starting from which the correcting values aredetermined.
 14. The method as recited in claim 9, wherein the correctingvalues are limited to admissible values.
 15. The method as recited inclaim 9, wherein the data are ascertained at certain test points.
 16. Adevice for controlling an internal combustion engine, including forcontrolling a fuel quantity injected, comprising: an arrangement for,starting from operating parameters, specifying a variable thatcharacterizes the fuel quantity, starting from which activating signalsfor an actuator are specified; and an arrangement for, starting from arotary speed, the variable characterizing the fuel quantity, and avariable characterizing a start of delivery, specifying correctingvalues for correcting the variable characterizing the fuel quantity.